For example, generally NbTi multifilamentary wires are utilized as windings of superconducting magnets to be used for nuclear magnetic resonance apparatuses and the like (see FIG. 16). The NbTi multifilamentary wire is small in magnetization of a winding since the diameter of one filament is so small as several to several ten micrometers. Liquid helium (with an atmospheric pressure boiling point of around 4 K) is used as a refrigerant for the NbTi multifilamentary wire. The liquid helium is expensive due to lack in resources, and there is a risk of exhaustion sooner or later.
Therefore, research and development for a nuclear magnetic resonance apparatus and the like utilizing a superconductor that is capable of possessing a superconducting property even with the use of a material abundant in resources such as liquid hydrogen (with an atmospheric pressure boiling point of around 20 K) and liquid nitrogen (with an atmospheric pressure boiling point of around 77 K) is in progress. A superconducting wire using these types of superconductors typically has a shape of a tape as shown in FIG. 17, and a superconducting layer thereof is around several millimeters in width, and around several to several hundred micrometers in thickness. Thus, when such a superconducting wire is used for a winding, magnetization of the winding becomes very large, and an electric current flowing in the winding becomes non-uniform due to a shielding current, whereby uniformity of the central magnetic field becomes diminished.
On the other hand, non-patent literatures 1 to 4 disclose dissertations regarding abnormal transverse-field effects, that is, when an AC magnetic field perpendicular to a DC transverse magnetic field is applied thereto, magnetization M in the direction of the DC magnetic field asymptotically varies with the periodic variation of the AC magnetic field; and when an amplitude of the AC magnetic field becomes larger than a certain value, the magnetization M is eliminated in a steady state. Further, non-patent literatures 5 and 6 disclose that the abnormal transverse-field effects are observed also in a tape-shaped superconducting wire.    NPTL 1: Kazuo Funaki and Kaoru Yamafuji, “Abnormal Transverse-Field Effects in Nonideal Type II Superconductors I. A Linear Array of Monofilamentary Wires”, Japanese Journal of Applied Physics, Vol. 21, No. 2, February 1982, pp. 299-304    NPTL 2: Kazuo Funaki, Teruhide Niidome and Kaoru Yamafuji, “Abnormal Transverse-Field Effects in Nonideal Type 2 Superconductors. II. Influence of Dimention Ratios in a Superconducting Ribbon”, Japanese Journal of Applied Physics, Vol. 21, No. 8, August 1982, pp. 1121-1126    NPTL 3: Kazuo Funaki, Minoru Noda and Kaoru Yamafuji, “Abnormal Transverse-Field Effects in Nonideal Type 2 Superconductors. III. A Theory for an AC-Induced Decrease in the Semi-Quasistatic Magnetization Parallel to a DC Bias Field”, Japanese Journal of Applied Physics, Vol. 21, No. 11, November 1982, pp. 1580-1587    NPTL 4: Kazuo Funaki, Teruhide Niidome and Kaoru Yamafuji, “Abnormal Transverse-Field Effects in Current Carrying Superconducting Wires”, Technology Reports of Kyushu University, Vol. 56, No. 1, January 1983, pp. 45-51    NPTL 5: Ernst Helmut Brandt and Grigorii P. Mikitik, “Why an ac Magnetic Field Shifts the Irreversibility Line in Type-II Superconductors”, Physical Review Letters, Vol. 89, No. 2, July 2002, 027002    NPTL 6: Ernst Helmut Brandt and Grigorii P. Mikitik, “Shaking of the critical state by a small transverse ac field can cause rapid relaxation in superconductors”, Superconductor Science and Technology, Vol. 17, No. 2, February 2004, pp. S1-S5